Nitrogen mineralization from rice straw as influenced by organic and inorganic amendments in acid soil

In a 90-day incubation study, we evaluated the effects of various organic and inorganic amendments [farm yard manure, microbial culture (MC) containing cellulose-degrading microorganisms (CDMs), earthworm culture (EWC), starter dose of inorganic N (urea) and lime] on N availability in an acid Inceptisol subsequent to rice straw incorporation under two soil moisture regimes (submerged and field capacity). In general, all the organic and inorganic amendments improved mineral N (NH4+-N + NO3--N) content in rice straw-amended soil; however, the biological agents (MC and EWC) were more effective than the starter dose of inorganic N. Combined application of MC+EWC proved to be the most effective under both moisture regimes, with the highest mineral N availability being observed after 60 days of incubation. Therefore, to synchronize the highest N demand of rice crop during its main growth period (nearly 60 days after transplanting) with the largest N availability in soil, incorporation of rice straw with CDMs and earthworms could be a viable rice straw management strategy in acidic soils of India.